There is a FreeRTOS demo for a TC1782 here: https://www.freertos.org/FreeRTOS-for-Infineon-TriCore-TC1782-using-HighTec-GCC.html I’m not sure how close that core is to the TC3xx core, but somebody on the forum recently ran the same port, or was able to modify the port, to run on a TC399xx.
We do not provide safety certification evidence for FreeRTOS, so if you wanted to use it in a safety environment you would need to do that yourself - however our strategic partner provides SafeRTOS (not open source) for Tricore that has various different safety certification packs.